Search

Biomolecular condensates comprised of specific proteins and nucleic acids are now recognized as one of the key organizing mechanisms in eukaryotic cells. However, the specific roles played by the nucleic acid secondary structure and sequence in biomolecular phase separation are still not clear. Here, utilizing giant membrane vesicles (GMVs) as a protocell model, we found that single-stranded DNA (ssDNA) with a parallel G-quadruplex structure could functionally cooperate with a G-quadruplex-binding protein to form speckle-like puncta inside the GMVs. The clustering behavior is dependent on the structural diversity of G-quadruplexes, and the reversible clustering behavior implicated a new pathway in dynamically regulating the formation of biomolecular condensates. This finding represents a potential link between G-quadruplex-binding proteins and the resulting G-quadruplex-mediated biomolecular phase separation, which would gain insight into a wide range of biological processes associated with nucleic acid-modulated phase separation inside living cells.

Engineering cell-derived nanovesicles with active-targeting ligands is an important strategy to enhance the targeting efficiency. However, the enhanced binding capability to targeting cells also leads to the binding with nontarget cells that share the same biomarkers. DNA-based logic gate is a kind of molecular system that responds to chemical inputs by generating output signals, and the relationship between the input and the output is based on a certain logic. Thus, the DNA-based logic gate could provide a new approach to improve the delivery efficiency of the nanovesicle. In this work, we developed a DNA logic-gated module that coupled two tumor cell-targeting factors (e.g., low pH and a tumor cell biomarker) in a Boolean manner. Immobilization of this module on the surface of the nanovesicle enables the nanovesicle to sense tumor cell-targeting factors and regard these cues as inputs AND logic gate. With the guide of DNA-based logic gate, gold carbon dots (GCDs) encapsulated within nanovesicles were delivered into target cells, and then the intracellular redox status variation was reflected by fluorescence change of GCDs. Overall, we developed DNA logic-gated nanovesicles that contract different targeting factors into a unique tag for target cells. This facile functionalization strategy can pave the way for constructing smart nanovesicles and would broaden their application in the field of precision medicine and personalized treatment.

Fluid Catalytic Cracking (FCC) has maintained its crucial role in refining decades after its initial introduction owing to the flexibility it has as a process as well as the developments in its key enabler, the FCC catalyst. Boron-based technology (BBT) for passivation of contaminant metals in FCC catalysts represents one such development. In this contribution we describe Fourier Transform Infrared Spectroscopy (FTIR) characterization of boron-containing catalysts to identify the phase and structural information of boron. We demonstrate that FTIR can serve as a sensitive method to differentiate boron trioxide and borate structures with a detection limit at the 1000 ppm level. The FTIR analysis validates that the boron in the FCC catalysts studied are in the form of small borate units and confirms that the final FCC catalyst product contains no detectable isolated boron trioxide phase. Since boron trioxide is regulated in some parts of the world, this novel FTIR methodology can be highly beneficial for further FCC catalyst development and its industrial application at refineries around the world. This new method can also be applied on systems beyond catalysts, since the characterization of boron-containing materials is needed for a wide range of other applications in the fields of glass, ceramics, semiconductors, agriculture, and pharmaceuticals.

Spatially resolved ambient pressure X-ray photoelectron spectroscopy has been used to measure and visualize regions of electrochemical activity, local surface potential losses, overpotentials, and oxidation state changes on single sided ceria/yttria-stabilized zirconia (YSZ)/Pt solid oxide electrochemical cells. When hydrogen electro-oxidation (negative applied bias) or water electrolysis (positive applied bias) is promoted on the ceria electrocatalyst, the Ce3+/Ce4+ ratios shift away from equilibrium values and thereby demarcate electrochemically active regions on the ceria electrode. In addition to the ceria oxidation state shifts, inactive surface impurities with high photoelectron cross sections, such as Si, can provide local markers of activity through chemical and surface potential mappings under various electrochemical conditions. Localized removal of chemically active carbonaceous surface impurities also reveals regions of electrochemical oxidation activity on the ceria electrode. Finally, we show...

Ambient pressure X-ray photoelectron spectroscopy was used to detect rigid shifts in photoelectron kinetic energies and material chemical states for operating solid oxide electrochemical cells. The kinetic energy shifts directly correspond to the surface electric potentials and therefore can be used to detect the local potentials / potential losses for operating cells. The ceria valence state changes under applied biases relative to equilibrium conditions (at open circuit voltage) reveal the electrochemically active regions ~150 μm away from the current collectors for ceria thin film electrodes. The results provide fundamental mechanistic information about the active length scales in ceria electrodes, the surface reaction kinetics, charge transport, as well as activities for oxidation and electrolysis on operating solid oxide electrochemical cells.

Thin-film GDC (Ce0.8Gd0.2O2-x 300 nm thick) electrodes with porous Ni or Au metal overlayers (300 nm thick) were sputter-deposited on polycrystalline YSZ substrates and tested in single-chamber cells. With a back-side Pt-counter electrode, the electrochemical cells were characterized by linear-sweep voltammetry and impedance spectroscopy between 650 to 750 ºC in mixtures of H2/H2O/Ar diluent. To complement the electro-chemical tests, ambient-pressure XPS at the Advanced Light Source was performed on active cells in H2/H2O mixtures to measure surface potential and oxidation states. The GDC electrodes showed lower resistance to H2O electrolysis than H2 oxidation with Ni and Au overlayers. XPS measurements indicated large overpotentials across the YSZ/GDC interface particularly for H2 oxidation on the GDC electrode. Increasing PH2/PH2O (up to 10) resulted in higher rates for not only H2 oxidation, but also H2O electrolysis, suggesting that H2O electrolysis activity is enhanced by increased reduction of the GDC surface.

Ambient pressure X-ray photoelectron spectroscopy (XPS) is used to measure near-surface oxidation states and local electric potentials of thin-film ceria electrodes operating in solid oxide electrochemical cells for H2O electrolysis and H2 oxidation. Ceria electrodes which are 300 nm thick are deposited on YSZ electrolyte supports with porous Pt counter electrodes for single-chamber tests in H2/H2O mixtures. Between 635 and 740 °C, equilibrium (zero-bias) near-surface oxidation states between 70 and 85% Ce3+ confirm increased surface reducibility relative to bulk ceria. Positive cell biases drive H2O electrolysis on ceria and further increase the percentage of Ce3+ on the surface over 100 μm from an Au current collector, signifying broad regions of electrochemical activity due to mixed ionic-electronic conductivity of ceria. Negative biases to drive H2 oxidation decrease the percentage of Ce3+ from equilibrium values but with higher electrode impedances relative to H2O electrolysis. Additional tests indic...

Heterogeneous films of ordered CeO(2)/Ni concentric nanostructures have been fabricated through template-assisted electrodeposition. The free-standing films of Ni metal (8 mum thickness) contain ordered arrays of ceria tubes (200 nm OD, 100 nm ID). Ni/CeO(2) coaxial nanotubes were also obtained by tuning experimental conditions. The interfacial contact area within the 3-dimensional oxide nanotube/nickel matrix is approximately 100 times greater than 2-dimensional thin films of nickel and ceria of the same area. The use of the film as an anode electrocatalyst/current collector is demonstrated in a solid oxide fuel cell.

The SbSI rodlike crystals with studded pyramids were synthesized from the reaction among antimony trichloride, thiourea, and excessive sodium iodide under moderate hydrothermal conditions at 200°C. The final products were characterized by XRD, SEM, XPS, and elemental analysis. The SEM images showed the SbSI rodlike crystals are inserted some octahedrons on the surfaces of the rods. Typically, the structure is 3–4 mm in length, 8–10 μm in diameter for a singular crystal. The size of the pyramids on the surface is about 10 μm in height and the length of hemline is 6–12 μm.

Through the use of ambient pressure X-ray photoelectron spectroscopy (APXPS) and a single-sided solid oxide electrochemical cell (SOC), we have studied the mechanism of electrocatalytic splitting of water (H2O + 2e(-) → H2 + O(2-)) and electro-oxidation of hydrogen (H2 + O(2-) → H2O + 2e(-)) at ∼700 °C in 0.5 Torr of H2/H2O on ceria (CeO2-x) electrodes. The experiments reveal a transient build-up of surface intermediates (OH(-) and Ce(3+)) and show the separation of charge at the gas-solid interface exclusively in the electrochemically active region of the SOC. During water electrolysis on ceria, the increase in surface potentials of the adsorbed OH(-) and incorporated O(2-) differ by 0.25 eV in the active regions. For hydrogen electro-oxidation on ceria, the surface concentrations of OH(-) and O(2-) shift significantly from their equilibrium values. These data suggest that the same charge transfer step (H2O + Ce(3+)-Ce(4+) + OH(-) + H(•)) is rate limiting in both the forward (water electrolysis) and reverse (H2 electro-oxidation) reactions. This separation of potentials reflects an induced surface dipole layer on the ceria surface and represents the effective electrochemical double layer at a gas-solid interface. The in situ XPS data and DFT calculations show that the chemical origin of the OH(-)/O(2-) potential separation resides in the reduced polarization of the Ce-OH bond due to the increase of Ce(3+) on the electrode surface. These results provide a graphical illustration of the electrochemically driven surface charge transfer processes under relevant and nonultrahigh vacuum conditions.